Using AATSR ADV (1995–2011) and MODIS C6.1 (2000–2017) annual and seasonal aerosol optical depth (AOD) aggregates, we obtained information regarding the occurrence of aerosols and their spatial and temporal variation over China. We specifically focused on regional differences in annual and seasonal AOD behavior for selected regions. AOD dataset comparisons, validation results and AOD tendencies during the overlapping period (2000–2011) are discussed.

The impact of desert dust on cloud formation is investigated for a major Saharan dust event over Europe by interactive regional dust modeling. Dust particles are very efficient ice nucelating particles promoting the formation of ice crystals in clouds. The simulations show, that the observed extensive cirrus development was likely related to the above-averge dust load. The interactive dust-cloud feedback in the model significantly improves the agreement with aircraft and satellite observations.

This study presents multiple years of aerosol coarse mode observations at the remote ATTO site in the Amazon Basin. The results are discussed in light of the frequent and episodic long-range transport of Saharan dust plumes in the early wet season as well as the persistent background bioaerosol cycling in the rain forest ecosystem. This work provides a solid basis for future studies on the dynamic coarse mode aerosol cycling and its biogeochemical relevance in the Amazon.

Fine particulate matter (PM) in the atmosphere is of concern due to its effects on health, climate, ecosystems and biological cycles, and visibility.
These effects are especially important in the Mediterranean region. In this study, the air quality model Polyphemus is used to understand the
sources of inorganic and organic particles in the western Mediterranean and evaluate the uncertainties linked to the model parameters and hypotheses related to condensation/evaporation in the model.

Lidar measurements of two expeditions across the Atlantic Ocean aboard the research vessel Polarstern are presented. In addition to Saharan dust layers and complex dust–smoke mixtures, pure marine conditions with enhanced particle depolarisation ratios on top of the marine boundary layer could be observed. A statistical analysis shows latitudinal differences in the optical properties within the marine boundary layer and illustrates the potential of these properties for aerosol classification.

In this work, the MACC reanalysis dust product is evaluated over Europe, Northern Africa and the Middle East using the EARLINET-optimized CALIOP/CALIPSO pure dust satellite-based product LIVAS (2007–2012). As dust plays a determinant role in processes related to weather and climate, human healt, and the economy, it is obvious that adequately simulating the amount of dust and its optical properties is essential. Our results could be used as a reference in future climate model evaluations.

This work focuses on the study of the sources and fates of BVOCs and new particle formation (NPF) events in the Eastern Mediterranean. NPF events were found on 14 out of 20 days of the campaign. NPF occured at various condensational sink and both under polluted and clean atmospheric conditions. Analysis of specific NPF periods of the mixed influence type highlighted that BVOC interactions with anthropogenic compounds enhanced nucleation formation and growth of newly particles.

A new aerosol typing algorithm based on artificial neural networks (ANNs) has been developed. The algorithm is providing the most probable aerosol type based on EARLINET LIDAR profiles. The ANNs used by the algorithm were trained using synthetic data, for which a new aerosol model has been developed. Blind tests on EARLINET data samples showed the capability of the algorithm to retrieve the aerosol type from a large variety of data, with different quality and physical content.

This investigation presents the variability in near-surface in situ aerosol particle light-scattering measurements obtained over the past decade at 28 measuring atmospheric observatories which are part of the ACTRIS Research Infrastructure, and most of them belong to the GAW network. This paper provides a comprehensive picture of the spatial and temporal variability of aerosol particles optical properties in Europe.

In this paper, particle fall streaks are analyzed to understand ice particle growth processes within precipitating mixed-phase cloud systems. The analysis is done by rearranging spectral polarimetric radar measurements along the retrieved fall streaks. Therefore, it is possible to identify and study the growth of single ice particle populations from the top to the bottom of the cloud system. The results show that such small scale processes can be analyzed using a precipitation radar.

A stand-alone automatic method for typing observations of the European Aerosol Research Lidar Network (EARLINET) is presented. The method compares the observations to model distributions that were constructed using EARLINET pre-classified data. The algorithm’s versatility and adaptability makes it suitable for network-wide typing studies.

The presented calibration method grants access to quality approved automated atmospheric water vapor profiles from lidar measurements. This method uses the Raman lidar data from the water vapor and nitrogen channels and additional data from sun photometer and GDAS. The retrieved water vapor profiles agree well with respective profiles from radio soundings. The paper describes this method and shows results from the CyCARE (Cyprus Cloud Aerosol and Rain Experiment) campaign in 2015–2017.

This paper presents different depolarization calibration procedures used to improve the quality of the depolarization data. The results illustrate a significant improvement of the depolarization lidar products for all the selected EARLINET lidar instruments. The calibrated volume and particle depolarization profiles at 532 nm show values that fall within a range that is accepted in the literature. The depolarization accuracy estimate at 532 nm is better than &pm;0.03 for all cases.

The high potential of the MPLNET polarized Micro-Pulse Lidar (P-MPL) in synergy with the POLIPHON (POlarization-LIdar PHOtometer Networking) method to retrieve the vertical separation of both the optical and mass features of the dust, smoke and pollen components mixed with other aerosols is demonstrated. This synergetic procedure can be easily applicable to the world-wide MPLNET lidar systems and also to spaceborne lidars: the ongoing NASA CALIPSO/CALIOP, and the forthcoming ESA EarthCARE/ATLID.

In this study we investigate the climatological behavior of the aerosol optical properties over Thessaloniki during the years 2003–2017. For this purpose, measurements from two individual networks, the European Lidar Aerosol Network (EARLINET) and the Aerosol Robotic Network (AERONET) were deployed. The analysis implies that the EARLINET sampling schedule can be quite effective in producing data that can be applied to
climatological studies.

The complementary use of two sensors, ATSR and MODIS, to provide aerosol information over two decades (1995–2015) is described. To this end, the AOD retrieved from both instruments had to be compared, showing that ATSR slightly underestimates and MODIS overestimates by a similar amount. Results show the increase of aerosols over the years, with an indication of the onset of a decrease in recent years. The AOD spatial distribution shows seasonal variations across China.

We provide a 3-D climatology of desert dust aerosols over South and East Asia, based on 9 years of CALIPSO observations and an EARLINET methodology. The results provide the horizontal, vertical and seasonal distribution of dust aerosols over SE Asia along with the change in dust transport pathways. The dataset is unique for its potential applications, including evaluation and assimilation activities in atmospheric simulations and the estimation of the climatic impact of dust aerosols.

The Generalized Aerosol Retrieval from Radiometer and Lidar Combined data algorithm (GARRLiC) and the LIdar-Radiometer Inversion Code (LIRIC) provide the opportunity to study the aerosol vertical distribution by combining ground-based lidar and sun-photometric measurements. Here, we utilize the capabilities of both algorithms for the characterization of Saharan dust and marine particles, along with their mixtures, in the south-eastern Mediterranean.

A retrieval method exploiting a synergy of radar, lidar, and microwave radiometer measurements is developed to simultaneously derive microphysical properties of cloud and drizzle in a physically consistent way. After successful tests with simulated scenes, this technique is applied to data collected in Cabauw, the Netherlands. Evaluation of the results shows that the retrieved cloud and drizzle properties are consistent with what is derived from multiple independent retrieval methods.

The Central Asian Dust Experiment provides unprecedented data on vertically resolved aerosol optical properties over Central Asia from continuous 18-month polarization Raman lidar observations in Dushanbe, Tajikistan. Central Asia is affected by climate change (e.g. glacier retreat) but in a large part missing vertically resolved aerosol measurements, which would help to better understand transport of dust and pollution aerosol across Central Asia and their influence on climate and health.

We conducted the first field measurements of non-refractory fine aerosols (NR-PM2.5) in a megacity of eastern China using a PM2.5-ACSM along with a PM1-ACSM measurement. Inter-comparisons demonstrated that the NR-PM2.5 components can be characterized. Substantial mass fractions of aerosol species were observed in the size range of 1–2.5 μm, with sulfate and SOA being the two largest contributors. The impacts of aerosol water driven by secondary inorganic aerosols on SOA formation were explored.

The depolarization ratio and the backscatter coefficient of marine particles are correlated with the relative humidity. The measurements were performed under atmospheric conditions with a multi-wavelength lidar system in pure marine conditions over Barbados in February 2014. For RH
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An intensive field campaign was conducted in March 2015 in the Eastern Mediterranean region, at a background site of Cyprus. We performed a detailed analysis of the chemical composition of air masses in gas and aerosol phase, and we applied a source apportionment analysis in order to identify the various origins of VOCs. The results suggest that VOCs are mainly of biogenic and regional background origins.

Our measurements performed with a lidar on Barbados give a vertical profile of Saharan dust, which was transported over 5000 km across the Atlantic. The new triple-wavelength depolarization technique reveals more information about the shape and size of dust, which will improve our understanding of the aging process of dust in the atmosphere and its representation in dust models. Changing properties of dust particles influence the solar radiation and the cloud properties and thus our climate.

A novel technique for multiwavelength lidars is introduced to derive information on the particle type in the tropospheric profile in analogy to the Cloudnet target classification. Four different aerosol classes and several cloud classes are defined. The technique is based on absolute calibrated lidar signals in temporally high resolution and thus is also well suited for aerosol–cloud-interaction studies. The approach was applied on a 2-month data set of the HOPE campaign in western Germany.

The ChArMEx SOP2 field campaign took place from 15 July to 5 August 2013 in the western Mediterranean Basin at Ersa, a remote site in Cape Corse. Exhaustive descriptions of the chemical composition of air masses in gas and aerosol phase were performed. An analysis of these measurements was performed using various source-receptor approaches. This led to the identification of several factors linked to primary sources but also to secondary processes of both biogenic and anthropogenic origin.

We study the impact of dust on solar energy using remote sensing data in conjunction with synergistic modelling and forecasting techniques. Under high aerosol loads, we found great solar energy losses of the order of 80 and 50% for concentrated solar power and photovoltaic installations, respectively. The 1-day forecast presented an overall accuracy within 10% in direct comparison to the real conditions under high energy potential, optimising the efficient energy planning and policies.

Vertical air motion is a key driver of physical processes in clouds. The stability of clouds and the process of ice formation have been shown to depend critically on vertical air motions. However, observations of vertical air motions and ice formation in clouds are rare. This motivated us in the Up- and downdraft in Drop and Ice Nucleation Experiment (UDINE) to deliver a comprehensive statistics, connecting remote-sensing observations of vertical motions and ice formation.

Strong events of biomass burning aerosol transported from North American forest fires were detected during July 2013 at three European stations from EARLINET. Satellite observations and models were used to estimate the smoke sources and transport paths. Using lidar techniques and regularization algorithms, the aerosol layers were optically and microphysically characterized, finding some common features among the events, concerning the similar aging processes undergone by the particles.

We provide a 3D multiyear analysis on the evolution of Saharan dust over Europe, using a dust product retrieved from the CALIPSO satellite and using EARLINET methods. The results reveal for the first time the 9-year 3D seasonal patterns of dust over its transport paths from the Sahara towards the Mediterranean. The dataset is unique with respect to its potential applications, including the evaluation of dust models and the estimation of ice nuclei concentration profiles from space.

The STRAP campaign was conducted in 2015 to investigate the volcanic plumes of Piton de La Fournaise (La Réunion, France). For the first time, measurements were conducted at the local (near the vent) and regional scales around the island. The STRAP 2015 campaign gave a unique set of multi-disciplinary data that can now be used by modellers to improve the numerical parameterisations of the physical and chemical evolution of the volcanic plumes.

This article provides an overview of the instrumental setup and the main results obtained during the two HD(CP)2 Observational Prototype Experiments HOPE-Jülich and HOPE-Melpitz conducted in Germany in April–May and Sept 2013, respectively. Goal of the field experiments was to provide high-resolution observational datasets for both, improving the understaning of boundary layer and cloud processes, as well as for the evaluation of the new ICON model that is run at 156 m horizontal resolution.

In this paper we present data of ice-nucleating particles (INPs) from a 1-month campaign in the Eastern Mediterranean using unmanned aircraft systems (UASs, drones) and offline sampling with subsequent laboratory analysis. To our knowledge, this is the first time INPs were measured onboard a UAS. We find that INP concentrations were 1 magnitude higher aloft than at the ground, highlighting that surface-based measurement of INP may only be of limited significance for the situation at cloud level.

An extreme dust storm affected Middle East and the Eastern Mediterranean in September 2015. This event was produced by a combination of meteorological and land-use properties. Analysis with remote sensing observations and modeling simulations reveals (i) transport of warm moist air from the Red and Arabian seas, (ii) formation of a thermal low over Syria, (iii) convective outflows and haboob formation (i.e. propagating dust walls), and (iv) changes in land-use and dust erodibility due to war.

Black carbon measurements are usually conducted with absorption filter photometers, which are prone to the filter-loading effect – a saturation of the instrumental response due to the accumulation of the sample in the filter matrix. In this paper, we conducted several field campaigns to investigate the hypothesis that this filter-loading effect depends on the optical properties of particles present in the filter matrix, especially on the coating of black carbon particles.

We derive the first comprehensive statistics of cirrus clouds over a tropical rain forest. Monthly frequency of occurrence can be as high as 88 %. The diurnal cycle follows that of precipitation, and frequently cirrus is found in the tropopause layer. The mean values of cloud top, base, thickness, optical depth and lidar ratio were 14.3 km, 12.9 km, 1.4 km, 0.25, and 23 sr respectively. The high fraction (42 %) of subvisible clouds may contaminate satellite measurements to an unknown extent.

We have developed artificial neural network algorithms to retrieve aerosol layer height from satellite OMI observations of the 477 nm O2–O2 spectral band. Based on 3-year (2005–2007) cloud-free scenes over north-east Asia, the results show uncertainties of 260–800 m when aerosol optical thickness is larger than 1. These algorithms also enable aerosol optical thickness retrievals by exploring the OMI continuum reflectance. These results may be used for future trace gas retrievals from TROPOMI.

The composition of fine particulate matter (PM) in two major Greek cities (Athens and Patras) was measured during two wintertime campaigns in 2012 and 2013. Residential wood burning has dramatically increased due to the Greek financial crisis, contributing around 50 % of the fine PM on average and more than 80 % during nighttime. Cooking is also an important source during both midday and evening, while transportation dominates only during the morning rush hour.

Dust is the most abundant aerosol in the atmosphere, considerably affecting Earth's climate. We use a new dust size discretization that improves the physical representation of dust in a regional climate model. This study is among the first studies evaluating the vertical profile of simulated dust with a pure dust product. The new dust size discretization increases dust optical depth by 10 % over the desert and Mediterranean. Consequently, the dust SW and LW radiative forcing is enhanced by 10 %.

To study aerosol transport in the Saharan Air Layer (SAL) from Africa to the Caribbean, we combine advanced optical models of Saharan aerosols with Stokes settling and two hypotheses about the occurrence of vertical mixing. By testing our hypotheses with lidar and in situ profiles measured near the top of the transported SAL, we find strong evidence that vertical mixing occurs in the SAL over the Atlantic with significant consequences for size distribution of the transported Saharan aerosols.

Aerosols play an important role in the Earth's climate. One of the main aerosol properties is the single scattering albedo which is a measure of the aerosol absorption. In this work we have presented a method to retrieve this aerosol property in the ultraviolet and we presented the results for measurements at the urban environment of Athens, Greece. We show that the spectral dependence of the aerosol absorption in the VIS–IR and the UV range depends on the aerosol composition and type.

There are many studies which show discrepancies between modeled and measured nitrous acid (HONO, precursor of OH radical) in the troposphere but with no satisfactory explanation. Ideal conditions to study the unknown sources of HONO were found on Cyprus, a remote Mediterranean island. Budget analysis of trace gas measurements indicates a common source of NO and HONO, which is not related to anthropogenic activity and is most likely derived from biologic activity in soils and subsequent emission.

In this work, single pixel observations from MODIS Terra and Aqua are analyzed together with data from other satellite sensors, reanalysis projects and a chemistry–aerosol-transport model to study the spatiotemporal variability of different aerosol types. The results are in accordance with previous works and are a good reference for future studies in the area focusing on aerosols, clouds, radiation and the effects of particle pollution on human health.

This work analyses the lidar polarizing sensitivity by means of the Stokes–Müller formalism and provides a new tool to quantify the systematic error of the volume linear depolarization ration (δ) using the Monte Carlo technique. Results evidence the importance of the lidar polarizing effects which can lead to systematic errors larger than 100 %. Additionally, we demonstrate that a proper lidar characterization helps to reduce the uncertainty.

Dual-wavelength depolarization sensitive Raman lidar measurements were used to characterize the optical properties of the dust loaded convective boundary layer over the Caribbean. Furthermore we derived the dust volume fraction and dust mass concentration within the convective boundary layer.

We probe thin layered clouds with remote sensing instruments from ground in order to get insight into atmospheric processes like the formation of rain or snow. We think that the findings of our work can be used to improve climate and weather simulations. The present paper presents a new technique that can be used to detect the shape, fall speed and mass of ice particles falling from layered clouds. With such information the impact of cloud ice, e.g., on the lifetime of a cloud, can be estimated.

This paper presents ﬁrst quantitative estimations of ice particle shape at the top of liquid-topped clouds. The estimation is based on polarimetric measurements from a Ka-band cloud radar. 22 cases observed during the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) campaign were used. Data from a free-fall chamber were used for the comparison. A good agreement of detected shapes with known shape–temperature dependencies observed in laboratories was found.

This study presents the 3-D structures of intense Mediterranean desert dust outbreaks, over the period Mar 2000–Feb 2013. The desert dust (DD) episodes are identified through an objective and dynamic algorithm, which utilizes satellite retrievals (MODIS, TOMS and OMI) as inputs. The performance of the satellite algorithm is evaluated vs. AERONET and PM10 data. The geometrical characteristics of the identified DD episodes are analyzed using the collocated CALIOP profiles as a complementary tool.

We present an automated software tool for the retrieval of profiles of optical particle properties from lidar signals. This tool is one of the modules of the Single Calculus Chain of the European Aerosol Research Lidar Network (EARLINET). It allows for the analysis of the data of many different lidar systems of EARLINET in an automated, unsupervised way.

Mineral dust content in PM10 was analysed at 20 regional background sites across Europe. Higher dust loadings were observed at most sites in summer, with the most elevated concentrations in the southern- and easternmost countries, due to external and regional sources. Saharan dust outbreaks impacted western and central European in summer and eastern Mediterranean sites in winter. The spatial distribution of some metals reveals the influence of specific anthropogenic sources on a regional scale.

A new algorithm allowed to retrieve aerosol optical depths from a Brewer spectrophotometer in Athens with excellent agreement with AERONET. The instrument radiometric stability and the performances of in situ Langley extrapolations as a way to track it are investigated. Potential sources of error and recommendations to operators are reported. MkIV Brewers represent a great source of information about aerosols in the past decades and a promising worldwide network for coordinated AOD measurements.

The findings from more than 10 years of global aerosol lidar measurements with Polly systems are summarized, and a data set of optical properties for specific aerosol types is given. An automated data retrieval algorithm for continuous Polly lidar observations is presented and discussed by means of a Saharan dust advection event in Leipzig, Germany. Finally, a statistic on the vertical aerosol distribution including the seasonal variability at PollyNET locations around the globe is presented.

The atmospheric science community demands for autonomous and quality-assured vertically resolved measurements of aerosol and cloud properties. For this purpose, a portable lidar called Polly
was developed at TROPOS in 2003. This lidar type was continuously improved with gained experience from EARLINET, worldwide field campaigns, and institute collaborations within the last 10 years. We present recent changes to the setup of our portable multiwavelength Raman and polarization lidar PollyXT.

This paper presents a detailed description of LIRIC (LIdar-Radiometer Inversion Code) algorithm for simultaneous processing of coincident lidar and radiometric observations for the retrieval of the aerosol concentrations. As the lidar/radiometric input data we use measurements from European Aerosol Research Lidar Network (EARLINET) lidars and collocated sun-photometers of Aerosol Robotic Network (AERONET). The LIRIC software package was implemented and tested at a number of EARLINET stations.

We introduce the quality-assurance efforts of the European Aerosol Research Lidar Network (EARLINET) at instrument level. Within several campaigns, 21 EARLINET systems from 18 EARLINET stations were intercompared. A comprehensive strategy for campaign setup and data evaluation was established. The intercomparisons have reinforced our confidence in the EARLINET data quality and allowed us to draw conclusions on necessary system improvements and to identify major challenges for our future work.

Satellite-derived products must undergo data evaluation with reference data sets in order to identify any possible reasons of discrepancy or to assess their representativity. In that direction, data coming from CALIPSO satellite were compared with observations from the ground. We identified a CALIPSO underestimation that could be linked to an assumption in the satellites' algorithms. The proposed correction improves the performance and could enhance aerosol modeling.

This study aims to present techniques developed to calibrate the lidar depolarization channels.
The experimental approach of the paper is designed to present how calibration procedures are implemented. Most of the literature is focused on the theoretical perspective of the topic and practical issues usually remain an open topic. A hands on approach for the assessment of the lidar polarization sensitivity is welcomed since most of these techniques require comprehensive practical description.

Large eddy simulations (LESs) are performed for the area of the Caribbean island Barbados to investigate island effects on boundary layer modification, cloud generation and vertical mixing of aerosols. Incoming Saharan dust layers are analyzed and effects of layer thinning, subsidence and turbulent downward transport become apparent, which are sensitive to atmospheric stability and wind shear. Comparisons of LES model output with lidar data systems are made to validate the modeling results.

A large intercomparison study of 13 Q-ACSM was conducted for a 3-week period in the region of Paris to evaluate the performance of this instrument and to monitor the major NR-PM1 chemical components. Reproducibility expanded uncertainties of Q-ACSM concentration measurements were found to be 9, 15, 19, 28, and 36% for NR-PM1, NO3, OM, SO4, and NH4, respectively. Some recommendations regarding best calibration practices, standardized data processing and data treatment are also provided.

In the framework of the ACTRIS summer 2012 measurement campaign (8 June–17 July 2012), EARLINET organized and performed a controlled exercise of feasibility to demonstrate its potential to perform operational, coordinated measurements and deliver products in near-real time. The paper describes the measurement protocol and discusses the delivery of real-time and near-real-time lidar-derived products.

In June and July 2013 dual-wavelength lidar measurements were performed in Barbados to study long-range transported Saharan dust across the Atlantic Ocean and investigate transport-induced changes. The focus of our measurements is the intensive optical properties, the lidar ratio and the particle linear depolarization ratio. While the lidar ratio shows no differences compared to the values of fresh Saharan dust, the particle linear depolarization ratio shows slight differences.

The paper combines remote sensing observations and detailed cloud modeling. It was shown that the main features of the observations could be captured which allows one to perform sensitivity studies. Those show that the liquid phase is mainly determined by the dynamical parameters of the model, whereas the ice phase is dominated by microphysical parameters such as ice nuclei number and ice particle shape.

Case studies of combined vertical-velocity measurements of Doppler lidar, cloud radar and wind profiler are presented. The measurements were taken at the Meteorological Observatory, Lindenberg, Germany. Synergistic products are presented that are derived from the vertical-velocity measurements of the three instruments: a comprehensive classification mask of vertically moving atmospheric targets and the terminal fall velocity of water droplets and ice crystals corrected for vertical air motion.

We present a method to derive water vapour profiles from Raman lidar measurements calibrated by the integrated water vapour from a collocated microwave radiometer. These simultaneous observations provide an operational and continuous measurement of water vapour profiles. The stability of the calibration factor allows for the calibration of the lidar even in the presence of clouds. Based on this approach, water vapour profiles can be retrieved during all non-precipitating conditions.

LIVAS is a 3-D multi-wavelength global aerosol and cloud optical database optimized for future space-based lidar end-to-end simulations of realistic atmospheric scenarios as well as retrieval algorithm testing activities. The global database is based on CALIPSO observations at 532nm, while for the conversion at 355nm EARLINET data are utilized.

In this study we summarize 1 year of Raman lidar observations over South Africa. The analyses of lidar measurements presented here could assist in bridging existing gaps in the knowledge of vertical distribution of aerosols above South Africa, since limited long-term data of this type are available for this region. For the first time, we have been able to cover the full seasonal cycle on geometrical characteristics and optical properties of free tropospheric aerosol layers in the region.

In this study, we perform global validation of MODIS high-resolution (3 km) AOD over global land by comparing against AERONET measurements. The MODIS–AERONET collocated data sets consist of 161 410 high-confidence AOD pairs from 2000 to 2015 for Terra MODIS and 2003 to 2015 for Aqua MODIS. We find that 62.5 and 68.4 % of AODs retrieved from Terra MODIS and Aqua MODIS, respectively, fall within previously published expected error.

The aerosol layer height is one of four aerosol parameters which is needed to enhance our understanding of aerosols' role in the climate system. Both active and passive measurement methods may be used to estimate the aerosol layer height. Aerosol height estimates made from passive infrared and solar satellite sensors measurements are compared with satellite-borne lidar estimates. There is considerable variation between the retrieved dust heights and how they compare with the lidar.

The accurate monitoring of climate based on the use of low-cost and low-maintenance automatic system represents one of the challenges for the scientific community and instrument manufacturers for the next decade. In the frame of two experiments, INTERACT and INTERACT-II, taking place at CIAO (CNR-IMAA Atmospheric Observatory) in Tito Scalo, Potenza, Italy, commercial low-cost lidars have been compared with advanced lidar systems to assess their performances.

Aerosol layer height (ALH) was retrieved from the OMI 477 nm O2–O2 band and its spatial pattern evaluated over selected cloud-free scenes. We used a neural network approach previously trained and developed. Comparison with CALIOP aerosol level 2 products over urban and industrial pollution in east China shows consistent spatial patterns. In addition, we show the possibility to determine the height of thick aerosol layers released by intensive biomass burning events in South America and Russia.

Observations of multiwavelength Mie–Raman lidar during smoke episode over West Africa are compared with the vertical distribution of aerosol parameters provided by the MERRA-2 model. The values of modeled and observed extinctions at both 355 nm and 532 nm are also rather close. The model predicts significant concentration of dust particles inside the smoke layer. This is supported by a high depolarization ratio of 15 % observed in the center of this layer.

We study the collocation mismatch uncertainty related to validating coarse-resolution satellite-based aerosol data against point-like ground based measurements. We use the spatial variability in the satellite data to estimate the upper limit for the uncertainty and study the effect of sampling parameters in the validation. We find that accounting for the collocation mismatch uncertainty increases the fraction of consistent data in the validation.

This study presents a comparison between active (CALIOP) and passive (POLDER) remote sensing methods, developed for retrieving aerosol above-cloud optical and microphysical properties. Main results show a good agreement when the aerosol microphysics is dominated by fine-mode particles or coarse-mode dust or when the aerosol layer is well separated from the cloud below. The paper is also focused on understanding the differences between the retrievals and the limitations of each method.

Based on measurements with a ceilometer and from an air quality network, the relationship between the mixing layer height (MLH) and near surface concentrations of pollutants was investigated for summer 2014 in Berlin. It was found that the heterogeneity of the concentrations exceeds the differences due to different MLH retrievals. In particular for PM10 it seems to be unrealistic to find correlations between MLH and concentrations representative for an entire metropolitan area in flat terrain.

We study the impact of dust on solar energy using remote sensing data in conjunction with synergistic modelling and forecasting techniques. Under high aerosol loads, we found great solar energy losses of the order of 80 and 50% for concentrated solar power and photovoltaic installations, respectively. The 1-day forecast presented an overall accuracy within 10% in direct comparison to the real conditions under high energy potential, optimising the efficient energy planning and policies.

In this work we have given a contribution to better understand some of the properties of the desert dust plumes in the western Mediterranean, using both direct measurements and satellite observations. This study has mainly evidenced that satellite observations can provide information about the geographical provenance of dust. This is important because such variability is reflected in the way in which dust interacts with atmosphere and impacts over the observed infrared radiation from satellites.

The detection of volcanic ash plumes and knowledge of their properties have been of increasing interest due to the effect ash particles can have on the aviation industry. A new method is shown for use with hyperspectral satellite instruments, such as the Infrared Atmospheric Sounding Interferometer, to derive optical and physical properties of volcanic ash. The results are compared to ancillary data sources, showing good agreement, which indicates better characterisation of volcanic plumes.

Multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements were performed in the urban environment of Madrid, Spain, where Sahara dust intrusion sometimes occurs. The study shows a high performances in the retrieval of aerosol optical depth, the surface extinction coefficient and an elevated layer during dust episodes, validated by AERONET in situ and modeling data. It is essential to capture the extinction properties of both local aerosol and Saharan dust.

We compare stratospheric aerosol loading computed with a new computer algorithm with various established datasets to determine the overall agreement. Since the new results are based on observation of starlight through the Earth's atmosphere, various aspects of these measurements can influence the final results. A systematic analysis of these aspects, such as the star brightness and temperature, is carried out to see if, and how, they influence the agreement of the results with other datasets.

Aerosol optical depths derived by the OMI near-UV algorithm are evaluated against independent observations over the ocean. The comparison resulted in differences within the expected levels of uncertainty. In addition, in clear sky conditions, the retrieved AODs compare well with independent measurements but they are biased high in partially cloud-contaminated pixels. Additional sources of discrepancies are documented and will be corrected in future versions of the algorithm.

The Geostationary Ocean Color Imager (GOCI) is the first ocean color sensor in geostationary orbit. It enables hourly aerosol optical properties to be observed in high spatial resolution. This study presents improvements of the GOCI Yonsei Aerosol Retrieval (YAER) algorithm and its validation results using ground-based and other satellite-based observation products during DRAGON-NE Asia 2012 Campaign. Retrieval errors are also analyzed according to various factors through the validation studies.

We introduce the quality-assurance efforts of the European Aerosol Research Lidar Network (EARLINET) at instrument level. Within several campaigns, 21 EARLINET systems from 18 EARLINET stations were intercompared. A comprehensive strategy for campaign setup and data evaluation was established. The intercomparisons have reinforced our confidence in the EARLINET data quality and allowed us to draw conclusions on necessary system improvements and to identify major challenges for our future work.

A satellite based surface visibility retrieval has been developed for the GOES-R ABI instrument using MODIS proxy data and validated using independent ASOS surface visibility measurements. Variability in the frequency of clear sky (aerosol) surface visibility retrievals larger than 20 dV is shown to be correlated with seasonal and interannual variability in fire detections, illustrating the importance of smoke from wildfires in regional haze events.

This article presents validation results for stratospheric aerosol extinction profiles retrieved from limb-scatter measurements with the SCIAMACHY instrument on the Envisat satellite. The SCIAMACHY retrievals are compared to co-located measurements with the SAGE II instrument. Very good agreement to within about 15% is found in a global average sense at altitudes above 15 km. The article also presents sample results on the global morphology of the stratospheric aerosol layer from 2003 to 2011.

Clear communication of the uncertainty on data is necessary for users to make appropriate use of it. This paper discusses the representation of uncertainty in satellite observations of the environment, arguing that the dominant sources of error are assumptions made during data analysis. The resulting uncertainty may be more usefully represented using ensemble techniques (a set of analyses using different assumptions to illustrate their impact) than with traditional statistical metrics.

The primary objective of the Complex Aerosol Experiment was measurement of microphysical, chemical, and optical properties of aerosol particles in the surface air layer and free atmosphere. The measurement data were used to retrieve the whole set of aerosol optical parameters, necessary for radiation calculations. Three measurement cycles were performed within the experiment during 2013: in spring, summer (July), and in late summer/early autumn.

Whiteman, D., Melfi, S., and Ferrare, R.: Raman lidar system for the measurement of water vapor and aerosols in the Earth's atmosphere, Appl. Optics, 31, 3068–3082, https://doi.org/10.1364/AO.31.003068, 1992.

The paper's scope is to evaluate the performance of in situ atmospheric aerosol instrumentation on board unmanned aerial vehicles (UAVs) and the performance of algorithms used to calculate the aerosol mass from remote sensing instruments by comparing the two independent techniques to each other. Our results indicate that UAV-based aerosol measurements (using specific in situ and remote sensing instrumentation) can provide reliable ways to determine the aerosol mass throughout the atmosphere.

The paper's scope is to evaluate the performance of in situ atmospheric aerosol instrumentation...